A. Intermediate Transfer Members for Use with Indirect Printing Systems
The invention, in some embodiments thereof, relates to the field of printing and to intermediate transfer members of printing systems. The invention, in some embodiments thereof, relates to the field of polymers and, to adhesives for such polymers, to curable polymer compositions and cured elastomers thereof, useful for the preparation of an intermediate transfer member of a printing system and of a release layer thereof.
In the art of indirect printing it is known, during a printing cycle when a specific image is printed on a specific substrate, to:
a. apply at (e.g., an image forming station) one or more inks, (each ink comprising a coloring agent in a liquid carrier) as a plurality of ink droplets to form an ink image on the image transfer surface of a release layer of an intermediate transfer member;
b. while the ink image is being transported by the intermediate transfer member, evaporate the carrier to leave an ink residue film including the coloring agents on the image transfer surface; and
c. transfer (e.g., at an impression station) the residue film from the image transfer surface to the substrate (e.g., paper, cardboard, cloth), thereby printing the desired image on the substrate.
Typically, the inks are in an oil-based (e.g., in liquid electrographic printing (LEP)) or water-based carrier. Such liquid inks may be applied to the image transfer surface of the intermediate transfer member of such printing systems by ink jetting of ink droplets, typically in a drop on demand mode.
For better printing results, an additional step to the previously described process may be needed. For instance, in LEP technology it is known to use an energy generated physical conditioning of the intermediate transfer member prior to the application of the ink. This physical conditioning causes the formation of electrophoretic attraction between charged coloring agent particles in the ink and the laser exposed image forms on the surface of a transfer surface, thereby fixing the coloring agent particles to the release layer.
Chemical conditioning methods are also known, which generally include the application of a chemical agent to the surface of the intermediate transfer member prior to the application of the inks. Such agents usually interact chemically with molecules of the inks and therefore typically need to be present in significant amount (e.g., thick coating, high concentration, prolonged presence during the process, etc.)
An intermediate transfer member is typically a laminated drum or looped blanket, also called a belt, the outermost layer of which, (i.e., the layer that defines the image transfer surface to which the inks are applied and from which the residue film is released to print the image on the substrate) is called the release layer.
Any given release layer has a specific set of physical and chemical properties to allow printing of a desired quality. Such release layer properties, the importance of which may vary from a printing process to another, include for example:
an image transfer surface (to which the ink droplets are applied) having properties such as affinity and wettability to the inks so that applied ink droplets remain localized where applied without excess spreading or beading, and allowing the ink image to be neatly transferred to the substrate without leaving substantial residue on the image transfer surface;
sufficiently adhesive to other layers of the intermediate transfer member;
sufficiently compressible to conform to the surface of the substrate during transfer, while preventing any distortion of the residue film during transfer to the substrate;
sufficiently resistant to the method used to fix the ink image, including for instance the heat applied to evaporate the ink carrier, or inert to the conditioning method, if needed; and
sufficiently abrasion resistant and smooth to have a reasonably long life-time.
B. Protonatable Intermediate Transfer Members for Use with Indirect Printing Systems
The invention, in some embodiments thereof, relates to the field of printing and, more particularly, to intermediate transfer members of printing systems. The invention, in some embodiments thereof, relates to the field of polymers and, more particularly, to novel elastomers.
In the art of indirect printing it is known, during a printing cycle when a specific image is printed on a specific substrate, to:
a. apply one or more inks, (each ink comprising a coloring agent in a liquid carrier) as a plurality of ink droplets to form an ink image on the image transfer surface of a release layer of an intermediate transfer member;
b. while the ink image is being transported by the intermediate transfer member, evaporate the carrier to leave an ink residue film including the coloring agents on the image transfer surfaces; and
c. transfer the residue film from the image transfer surface to the substrate (e.g., paper, cardboard, cloth), thereby printing the desired image on the substrate.
Typically, the inks are applied by to the image transfer surface by ink jetting, typically at a printing or image forming station of a printing system, although other methods of applying ink may also be used.
Typically, the residue film is transferred from the image transfer surface to the substrate at an impression station of a printing system, by engaging the intermediate transfer member with an impression cylinder.
An intermediate transfer member is typically a laminated drum or looped blanket (also referred to as a belt) the outermost layer of which, (i.e., the layer that defines the image transfer surface to which the inks are applied and from which the residue film is released to print the image on the substrate) is called the release layer.
For various reasons, it is desirable to use ink compositions including a water-based rather than organic carrier. Known image transfer surfaces of known release layers are unsuitable for printing with such ink compositions.